The present invention relates in general to liquid crystal displays, and in particular to material structures and preparation methods for the alignment of the liquid crystal material that forms a portion of a liquid crystal display.
Liquid crystal display (LCD) technology is used worldwide in a variety of products ranging from watches through cellular phones to computers. The revenue associated with this industry is estimated to be several billion dollars annually.
An essential requirement, in the manufacture of liquid crystal displays, is the alignment of the liquid crystal molecules on the surfaces (hereinafter xe2x80x9calignment surfacexe2x80x9d) of a substrate (hereinafter xe2x80x9calignment layerxe2x80x9d). The liquid crystal molecules are placed on the alignment surface prior to the formation of the liquid crystal display cell. The pervasive method for producing such an alignment surface is to coat with a film, such as a polyimide film, and then rub the coated surface with a velvet cloth. This rubbing process realigns the polyimide surface to form the alignment surface. The alignment surface provides a directional template for the alignment of the liquid crystal molecules in contact with the surface.
The rubbing method has been the process of choice for the last three decades to provide the alignment surface required for LCD=s. However, its been recognized by the industry that a non-contact or a non-rubbed method of surface alignment is very desirable for future manufacturing. The rubbing process introduces debris from the cloth in an otherwise clean room environment. The rubbing process can also lead to electrostatic charge build up, which can destroy the transistors below the polyimide surface. Since these transistors are essential for the operation of modem liquid crystal display devices, it is especially important to provide a method of forming the alignment surface that does not threaten the viability of these transistors.
U.S. Pat. No. 5,770,826 to Chaudhari et al. shows a non-contact technique that uses a low energy ion beam to modify the surface of a wide class of materials to develop directionality useful in forming an alignment layer. This directionality, or orientational order, then aligns liquid crystal molecules. It has been shown that liquid crystal display panels can be built using these inventions.
A strong driving force in liquid crystal display technology is to improve the visual quality of the overall liquid crystal display panel. However, no method is known to control the parallelism of liquid crystals. Parallelism is a key factor to obtaining uniform liquid crystal display panel uniformity.
It is an object of the present invention to provide a method to form an alignment surface for use in a liquid crystal display cell.
It is also an object of the present invention to provide an improved non-contact method for preparing an alignment surface for a liquid crystal display cell.
It is still another object of the present invention to provide a method of determining at least one ion beam source operation parameter to achieve a twist angle that is less than a predetermined maximum twist angle.
It is yet another object of the present invention to provide a method of preparing an alignment surface for a liquid crystal display cell.
It is further an object of the present invention to provide an improved liquid crystal display cell and display.
The present invention, in brief summary, is a method for forming an alignment surface for use in a liquid crystal display that includes the steps of (1) providing a particle beam source having a plurality of particle beamlets emanating from a grid surface; (2) providing an alignment layer having a surface; and (3) exposing the alignment surface to the particle beam source to create an alignment surface. The step of exposing the alignment surface to the particle beam source further includes the initial steps of (3a) estimating a current density at the grid surface; (3b) using the estimated current density to estimate a beam divergence angle for each of the plurality of particle beamlets; (3c) calculating a dominant beam incident angle for the plurality of particle beamlets; and (3d) determining at least one ion beam source operation parameter to achieve a twist angle that is less than a predetermined maximum twist angle.